They Body Composition/Exercise Core will provide comprehensive body composition analysis together with the exercise testing components of this grant proposal. Dual energy x-ray absorptiometry will be used to measure bone mineral density, fat free mass, and regional fat mass. CT scanning will be used to quantitate visceral adipose tissue mass and skeletal muscle area in the thigh. Total body water (2/H20) and extracellular fluid space (bromide space technique) will be measured to assess the quality of fat free mass as determined by dual energy x-ray absorptiometry. This core will also perform measurements of peak oxygen uptake, isotonic and isometric strength. In addition, this core will provide support for the large number of indirect calorimetry measurements which will be required for Protocols I, III, and IV. This core has access to state-of-the-art instruments for body composition analysis together high quality strength testing facilities. The availability of both the equipment and the expertise to conduct the body composition and exercise portions of this grant proposal assures high quality testing of the participants in this study.